Fibroids or leiomyomas of uterus can be hypodense , isodense or hyperdense relative to normal contrast enhanced myometrium on CT scan.As you have not mentioned your menstrual history or obstetric history or the cause of CT scan done , so it is very difficult to co-relate the findings and to reach a diagnosis.

Other causes of hypodensity can be due to hydrometra or degeneration in fibroid , the possibilities of these two are very less.It is better to get 3D multiplanner scan done to see the saggital and coronal sections.If you can attach the reports it would be better for me to diagnose it properly.

There is nothing to worry about so just relaxBest wishes and take care